Dielectric drier having an adjustable exhaust system



y- 21951 Y B H. GRIFFITH, JR 2,560,763

DIELECTRIC DRIER HAVING AN ADJUSTABLE EXHAUST SYSTEM Filed Jan. 31, 1950 2 Sheets-Sheet 1 IL 25' a2 38 4/ July 17, 3951 B. H. GRIFFITH, JR ,5

DIELECTRIC DRIER HAVING AN ADJUSTABLE EXHAUST SYSTEM Filed Jan. 31, 1950 2 Sheets-Sheet 2 Patented July 17, 1951 DIELECTRIC DRIER HAVING AN ADJUST- ABLE EXHAUST SYSTEM Ben Griifith, J12, West Allis, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application January 31, 1950, Serial No. 141,463

7 Claims- This invention relates generally to improvements in dielectric heating means utilizing an alternating current voltage for heating nonconductive materials, and particularly to improvements in dielectric driers in which means are provided for collecting the moisture driven from moist nonconducting materials during heating.

In recent years dielectric heating has superseded gas or electric oven heating where a rapid and uniform distribution of heat throughout the mass of a nonconducting material is desired. It is possible 'by means of a dielectric heater or drier in which a moist nonconducting material is inserted between a pair of electrodes energized by ahigh frequency voltage to remove substantially all the moisture from the material within av matter of minutes. As an example, a green foundry sand core with a resin binder may be cured in a dielectric .drier in an average time of 12 minutes.

During the heating period, considerable (1,113.11: titles of water vapor may be liberated depending upon the amount of the material present. Ifhis released water vapor is initially above its dew point. Unless it is rapidly removed from the drier or unless heat is continually applied to the vapor it will fall below its dew point and condense on surrounding surfaces. If the water vapor condenses on the surface of an insulator, the deposited water film may be enough to induce an incipient are over. If the water vapor condenses on an electrode, the accumulation of water may be sufficient to form drops which in falling may also induce an are over, the are traveling between the electrodes over the surface of the material being heated.

The best way of avoiding arc overs is to prevent the condensate from forming. This may be done by collecting and removing the water vapor from the drier before it has the opportunity :to appreciably condense.

Heretofore, one way of accomplishing this has consisted of using a grid type upper electrode and allowing the water vapor, which is lighter than the surrounding air, to rise through the interstices of the grid and to be exhausted from the hood of the drier. To avoid premature condensation of the water vapor as it passes through the grid and before it reaches the exhaust system, it has heretofore been necessary to supply heat to the vapor by means of auxiliary heaters mounted in the drier. These auxiliary vheaters are usually in the form of steam p p or le ric resistance heaters. Since they are of negligible effect in heating the material to be dried, in c ntrast to the heat generated in the same material by the alternating voltage, the elimination of these heaters will result in a simpler, more compact, and less expensive dielectric drier- Hcretofore, another way thought to avoid arc overs between electrodes has been to blow by means of a forced draft, a stream of air betwe n the electrodes so as to disperse the water vapor as it is released from the material being heated, and then to exhaust the vapor by mean of an exhaust system mounted in the drier hood. I-, h is method has the disadvantage of filling the interior of the drier with water vapor and exposin insulator and upper electrode surfac s o he adverse effects of condensation. The arrangement has a further disadvantage in that i require a forced draft blower for forcin the mov ent oi air between the electrodes.

The present invention proposes to avoid hav-. ing to use in a dielectric drier either auxiliary heaters or a forced draft blower by providin means for collecting and removing water vapor released by the material being heated while the v p r i still contained between th electrodes and before it has had an opportun ty to cond nse on insulator or electrode surfaces. The inveno pr p ses to do this in a drier havi a pair of horizontally disposed planar electrodes vertical register by uiding the water vapor along the under surface of the upper electrode and into an exhaust system intake opening adjacent the under surface of the upper electrode and below the level of the electrode. The intake is adjustable together with the upper electrode so that for all spacings between electrodes the intake opening will always be in the same relative position adjacent and below the under urface of the upper electrode.

In brief the invention proposes to so coup the intake openin with the upp elec de that the intake opening w ll be tr ns te with the upper electrode the same amount for all adjustments of spacing between electrodes.

The present invention proposes to further prevent con ensation on the under surfac of th upper electrode by providin a moisture barr er nd c ndensati n inhi itin m ans in erposed between the upper electrode and the material be heated. This barrier is fastened to the upper ele trode and may be of the type of material havin the pr perty of initially absorbing enough of the released water vapor to cause it to be heated by the dielectric field. The temperature of the barrier will rise until .it reaches the vapor? ization temperature of the water vapor at which point it will absorb no more water vapor than it itself is releasing. The temperature then remains in equilibrium, being around 212 F. for atmospheric pressures, so long as the material being heated releases water vapor. When the electrode is equipped with such a moisture barrier the barrier cooperates with the intake opening by guiding the water vapor into the exhaust system.

It is therefore an object of the invention to provide an improved dielectric drier in which the number of parts is reduced and which in particular avoids the use of auxiliary heaters to prevent condensation in the drier.

Another object of the invention is to provide an improved dielectric drier in which the water vapor released from the material being heated is removed directly from the volumetric zone between the driers electrodes without having to pass through or by other portions of the structure of a the drier.

Another object of the invention is to provide an improved dielectric drier in which the water vapor released from the material being heated may be removed without recourse to blowing air between the electrodes.

Another'object cf the invention is to provide an improved dielectric drier in which there is an op- .timum transfer of water vapor from the region encompassed between the electrodes to the exhaust system regardless of the distance between electrodes.

' Another object of the invention is to provide an improved dielectric drier in which the water vapor released from the material being heated is guided by and under one electrode into an exhaust system regardless of the position of the one electrode with respect to the other electrode.

-" Another object of. the invention is to provide an improved dielectric drier in which the electrodes and insulators are protected from the adverse effects of condensation.

Another object of the invention is to provide an improved dielectric drier in which the water vareleased from the material being heated is utilizedto activate a moisture barrier and condensation inhibiting means for preventing condensation on one of the electrodes of the drier.

" Another object of the invention is to provide an improveddielectric drier in which the water vapor released from the material being heated is guided by a moisture barrier and condensation inhibiting means into the exhaust system regardless of the spacing between electrodes.

Objects and advantages other than those set forth will be apparent from the following description when read together with the accompanying drawings, in which:

Fig. 1 is a side View, partly in elevation and partly in section, showing one embodiment of the invention, a side panel and a portion of the tuning stub and upper electrode of the dielectric drier being removed to show the exhaust system intake opening;

Fig. 2 is a transverse section of the dielectric drier taken along line II-II in Fig. 1 showing the exhaust system intake opening positioned adjacent and belowthe level of the adjustable elec- 'trode;

I Fig. 3 is a transverse section similar to Fig. 2 through another embodiment of the invention showing an exhaust system with multiple intake openings positioned adjacent and below the level of the adjustable electrode and on either side thereof Fig. 4 is a transverse section similar to Fig. 2 through still another embodiment of the invention showing an exhaust intake element integral with and surrounding the adjustable electrode; and

Fig. 5 is a schematic view of the electrical circuit of the dielectric driers of Figs. 1 through 4.

The dielectric drier ll of Figs. 1 and 2 comprises an adjustable upper electrode 12 of the plate type and a fixed lower electrode 13 also of the plate type, the two electrodes l2, l3 extending in parallel spaced relation within the drier I I. The lower electrode [3 is substantially rectangular and is supported on a pair of longitudinally extending angle members M. The angle members I4 in turn are supported on a plurality of horizontally spaced legs l5. To prevent the lower electrode l3, which is formed of metal sheeting, from sagging along its longitudinal axis a plurality of transverse angle members [1 are used as reinforcing, the members ll extending in longitudinally spaced relation under the electrode I3 and beyond the legs [5 on either side of the drier.

The angle members l4, l1, legs [5, and lower electrode 13 are fastened where they come together, as by welding, so as to afford a rigid base structure 18 on which a linearly traveling .belt l9, preferably of the endless type, and of a material having a low electrical power loss, issupported. The base structure [8 is reinforced by a plurality of horizontal bracing members 28 which extend respectively longitudinally and transversely of the drier l l between the lower extremities of the legs l5. Gusset plates 22 provide further rigidity respectively between the legs l5 and bracing members 20 and between the legs l5 and longitudinally extending members l4.

Extending upward from the fixed electrode I3 is another supporting structure 23 comprising vertically extending angle members 24; longitudinally extending angle members 25', and transversely extending angle memberslfi which are fastened together to fomr the supporting-means or frame 23 on which insulating panels 21 are so fastened that the whole provides a'hood encompassing the electrodes. It will be apparent from the configuration 'of the drier. H, as shown in Figs. 1 and 2, that the hoodis provided with entrance and exit openings 29, 30 for conveying material 3| to be dried into and out of the space between the electrodes l2, l3.

The clearance between the electrodes I2, I3 is determined by the vertical height of the material 3l to be dried. (See Fig. 2.) To allow'for adjustment of this clearance, the upper electrode l2, which is substantially of rectangular shape, is supported from the frame 23 in the followin manner.

Depending from the transversely extending angle members 26 of the hood frame 23-are'a plurality of sheave hangers 32. Each hanger 32 supports a rotatable sheave 33 having a cable groove therein. The upper electrode l2, which is preferably made of aluminum sheeting 34 stretched over a reinforcing web is provided with vertical standoff insulators 35 to which lifting cables 31 are attached. Each cable 31 passes over a respective sheave 33 and thence to one of a plurality of winding drums 38 carried by'a transversely extending shaft 39 journalled in hangers 40 slung respectively from the longitudinally extending angle members 25 of the hood frame 23. A control hand wheel 4! is securely fastened to one end of the shaft 39. By means of this wheel the-shaft maybe-motated clockwise or counterclockwise, as viewed in Fig. l, to wind or unwind the cables 31 on the drums 38 thereby raising or lowering the upper electrode I2. Thus assembled, the sheaves 33, cables 31, drums 3.8, shaft 39 and wheel 4| provide means mounted on the supporting means or hood frame 23 for adjusting the spacing between the electrodes I2, l3 to accommodate varying sizes of moist objects 3|. And the endless belt I9 driven by propulsion means not shown provides movable means associated with the lower electrode I3 for introducing the objects to be dried between the electrodes.

To provide for the withdrawal of water and other vapors released from the material being dried, exhaust means 43 comprising an exhaust manifold 44 and an exhaust fan 45, the latter element being shown in the embodiment of Fig. 3, is included in the drier I I.

The exhaust manifold 44 of Figs. 1 and 2 is mounted on one side of the hood frame 23 and extends in a longitudinal direction parallel to the upper electrode I2 and in a vertical direction tow ard the top of the hood. A portion of the manifold 44 slopes upward from a point near either end of the hood to converge into an exhaust stack 46, which as shown in Fig. 3, is con- 'nected with the housing of the exhaust fan 45. For the sake of simplicity the exhaust fan 45 is shown only in Fig. 3 but it will be understood that the exhaust manifolds 44 of the embodiments of the other figures connect respectively with similar exhaust fans.

The exhaust manifold 44 is provided with a movable intake element 41 which extends parallel to the upper electrode I2 and slightly exceeds the electrode in length. The intake element 41 may be constructed, however, so that its length is less than that of the electrode I2. In which case the length of the manifold 44 is correspondingly reduced. This intake element 41 comprises a rectangular prismatic upper portion or shell 49 which telescopes into a slightly larger rectangular prismatic depending lower portion of the manifold 44. The clearance between the shell 49 and the manifold 44 is a minimum consistent with a freely sliding'fit.

The intake element 41 at its lower end is provided with a 90 degree elbow and a horizontally disposed stub extension 5|] which faces and opens toward a longitudinally extending edge 5| of the upper electrode I2. The port or opening 52 in the stub extension 56 of the intake element 41 is essentially rectangular and extends parallel to the longitudinally extending edge 5| of the upper electrode I2. As shown in Fig. 2, the opening .52 is adjacent the upper electrode I2 and :below the level of the electrode.

At each end :of the intake element 41, as shown in Fig. l, a cable 53 is fastened "to a lug 54 extending from the element 41. Each cable 53 rides over a rotatable sheave 55 carried by a hanger 56 slung from one of the longitudinally extending angle members v25. The other ends of the cables 53 are attached to respective winding drums 58 carried by the shaft 39. Since the diameter of the winding drums 58 to which the intake element cables 53 are fastened is equal to the diameter of the drums 38 carrying the electrode cables 31, the liftin of the electrode I2 up or down by a turn of the hand wheel 4| is accompanied :by a corresponding lifting up or down of theintake element 41.

Raising the upper electrode I2 say a distance of :four inches will result in raising the intake element 41 a corresponding distance; namely, four inches. Thus for all positions of the upper electrode I2 the intake element opening 52 will always be in the same relative position adjacent the upper electrode I2. The intake element opening 52 will always be just below the level of the upper electrode I2. The significance of this arrangement of intake opening to electrode will immediately become apparent when the operation of the drier is described. But before proceeding to th operation of the drier there are a few other details of construction that should be explained.

An examination of the upper electrode I2 illustrated in Figs. 1 and 2 will disclose that the metal sheeting 34 has been rolled up to give the elec trode I2 a continuous smooth surface along-all four edges. In this way the dielectric stresses when the electrode I2 is excited are apportioned over the rolled surfaces and not concentrated along sharp edges. Th net effect is to minimize the possibility of corona or are overs. I

The electrodes I2, I3 are excited from asource of high frequency voltage 59, as shown schematically in Fig. 5. The excitation circuit comprising the electrodes I2, I3 is tuned by means of a reactance loop or tuning stub 60 connected in parallel across the electrodes. The stub 60 comprises a U-shaped member held firmly in place at one side of the drier hood by means of fstandoff insulators GI which extend respectively from the hood frame 23 and the lower electrode I3. The stub 60 is provided with a movable shfunt 62 carried by the stub. By moving the shunt 62 along the stub 60 so as to short out a portion of the stub, the 'reactance of the loop may 'bevaried. A cable 63 for moving the shunt 62 is guided in sheaves 65 rotatably fastened to the frame 23, and the movement of the cabl 63 is controlled by a hand wheel 66 which is mountedat the lower edge of the drier hood below the electrode control wheel 4|. A spring 61 interposed between portions of the cable 63 maintains the tension of the cable 63 for all positions of the shunt 62 along the stub 66.

The lower electrode I3 is connected to ground and since the lower electrode I3 is part of the supporting structure I8 and connected to the frame 23, all the external portions of the drier I I will also be at ground potential.

The drier II operates in the following manner. The electrodes I2, I3 are adjusted for their correct spacing, after which they are energized from the source of high frequency voltage 59. Next the belt I9 is caused to move slowly between the electrodes I2, I3. At the same time the exhaust fan 45 is turned on. Moist objects 3| to be dried, such as green foundry sand cores, are placed on the belt I9 as indicated in Fig. 2, and pass through the opening 29 in the drier hoodinto the space between the electrodes I2, I3. The speed at which the belt I9 is caused to move between the electrodes I2, I3 is a, function of the amount of moist material on the belt I9, the quantity of moisture present in the material, and the upper temperature limit to which the material can be raised without exploding. When the dielectric drier is utilized in drying foundry sand cores, the belt speed selected may vary between 5 to 18 inches per minute.

During the interval the electrode spacing is being adjusted the exhaust intake element 41 will automatically follow the adjustable electrode I2. Thus for any selected spacing of electrodes I2, I3 the intake opening 52 will always be in the same .the intake opening 52.

.relative position adjacent the adjustable electrode I2 and just below the level of the electrode. The effect of having the intake element 41 followthe adjustable electrode I2 is to. establish a predetermined distance between the electrode l2 and the intake element opening 52 for all spacings of the electrodes l2, l3. Regardless of the spacing selected this distance will never vary. The importance of this arrangement will become apparent as the description proceeds.

water vapor. and other gases from the material.

The water vapor being lighter. than the surrounding air rises until it strikes the under surface of the upper electrode l2. haust fan 45 is operating to reduce the pressure in the exhaust manifold 44 the water vapor will be urged toward the opening 52 in the intake element 41 because of the lower pressure existing in this region. The water vapor will actu- 1 ally be caused to roll under the electrode 12 into The electrode I2 thus acts as a barrier or guide cooperating with the exhaust manifold intake 51 to get the water vapor from the space between the electrodes l2, l3 into .the exhaust manifold 44 before the water vapor has a chance to spread out under the hood and condenseon the insulators 35 or the electrodes l3. Since the intake opening 52 is always at the same predetermined trode l2 for all spacings of the electrode l2, and

:since this distance is selected as a minimum commensurate with'the voltage gradient existing between the electrode l2 and the frame 23, the intake opening '52 is in the optimum position to capture substantially all the vapor released by the material being heated.

To suppress any possibility of condensation on the upper electrode it may be desirable to further provide the electrode with a moisture barrier and condensation inhibiting means 83. This barrier 68 will take the form of a thin layer of non-- conducting material having a relatively low power loss in an alternating dielectric field. The material utilized in the barrier may be of the type having the property of initially absorbing enough of the released water vapor to cause the material to become heated to a temperature around 212 F. Once the barrier 68 reaches this temperature, the absorbtion by and release of water vapor from the barrier will be in equilibrium and the heat of the barrier will prevent xcond'ensate from collecting on its surface.

01' the barrier 68 may simply be made of a nonhygroscopic low loss material which will become sufficiently heated in the alternating dielectric field to prevent condensation on its surface. When the electrode I2 is equipped with a moisture barrier.,'as shown in Figs. 1 and 2, the barrier 68 acts as a guide cooperating with the exhaust manifold intake 41 to get the released water vapor from the space between the e1ectrodes I2, 13 into the exhaust manifold M.

The drier 69 shown in 3 is similar to the drier H shown in Fig. 2 except that an addi tional exhaust intake element M has been provided on the other side of the drier opposite the intake element The additional intake element 47 is coupled to the upper electrode 12 in exactly the same manner the intake ele- Since the ex-' distance from the elec- .i

8 merit 41 of the drier ll of Fig. 2 is coupled to the electrode l2 of Fig. 2. However, the addition of another exhaust manifold 44' and the intake element 47' to the drier necessitates a rearrangement of certain components of the drier.

As shown in Fig. 3, the added exhaust manifold M is supported by a subframe l fastened respectively to one of the sides and the top of the hood frame 23. The tuning stub 12 of the drier of Fig. 3 has been lowered from the position shown in Fig. 2 to a position just below the lower electrode l3 and to one side of the supporting legs l5. This shift of the tuning stub necessitated extending one side of the hood frame 23 to the fioor level and joining it to the legs l on one side of the drier by means of bracing members l3 placed between the extended side and the legs l5.

The two exhaust manifolds 44, 44 of the drier of Fig. 3 are joined by extending the stacks 46, 46 over the top of the drier hood and meeting at the exhaust fan 45. Since the intake elements 61, 41 of the exhaust manifolds M, 44' are coupled to the electrode l2 in the same manner as the corresponding elements of the drier of Fig. 2 any adjustment of the upper electrode l2 will cause the intake elements 41, H to follow the electrode I: so as to always present the intake openings 52, 52' in the same relative position adjacent the electrode 12 and below the surface of the electrode, as shown in Fig. 3.

The addition of the second intake element 4'! adjacent the electrode 12 but opposite the first intake element 41 reduces the opportunity for any water vapor to escape upward around the side of the electrode l2 and permits the design of driers having a greater width of electrode surface. v

The driers of Figs. 1 and 3 may be simplified by going to the embodiment .of Fig. 4' in which, an exhaust manifold 14 is draped over the upper electrode H. In this embodiment the electrode 12 is mounted as described hereinbefore in con,- nection with the driers of Figs. 1 and 3. Buttthe exhaust means differs from the exhaust means of the other embodiments in the following manner.

A longitudinally extending canopy "15 either of metal or insulating material is draped over the upper electrode I2 so as to extend beyond the edges of the electrode on all four sides and to afford a conduit passage 16 between the canopy T5 and the electrode l2. The canopy 15 may be provided on its upper surface with a plurality of apertures 11 through which vertical standoff insulators of the upper electrode l2 extend. The apertures 11 are equipped with insulating and sealing grommets 19 which grip the insulators 35 tightly to securely hold the canopy 15 in spaced relation with the electrode l2. Although the insulators 35 in Fig. 4 are shown as piercing the canopy 15 to meet the electrode l2, the insulators 35 may be mounted instead directlyon the canopy T5, in which case spacers are inserted between the canopy and the electrode to provide the conduit passage 15.

At its center the canopy 15 is pierced and rimmed over to provide an opening in the top for connection to an exhaust manifold 8|. Attached to this opening is a vertically extending shell type insulator 82 having its outer surface corrugated to afford a long leakage path between the canopy l5 and the exhaust manifold 8|. .The shell type insulator 82 has an internal dimension so selected that a lower portion of the exhaust manifold 8] follows the. contour. thereof and is connected with an exhaust fan, not shown,

which may be of the type illustrated in Fig. 3.

With the arrangement shown in Fig. 4, it is possible to eliminate the intake element cables 53 of Figs. 1 and 2 and use the electrode cables 31 to support both the canopy 15 and the upper electrode.

When the dielectric drier of Fig. 4 is operating, the released Water vapor striking the upper electrode I2 is drawn into openings 83 adjacent the edges of the electrode l2 and travels through the passage 16 formed by the walls of the canopy l5 and the electrode [2" into the exhaust manifold 8| Since the canopy I5 is securely rastened to the electrode l2 it will move with the electrode for all changes in the spacing between the electrodes l2, l3 and thus the exhaust intake opening 83 will always be in a position to withdraw released water vapor which collects in the space between the electrodes.

Although the invention is illustrated as in,- corporated in a dielectric drier having plate type electrodes, it is equally well suited for use in a drier having electrodes of other contours. And the invention lends itself for use in dielectric driers in which a circular feeding table is substituted for the linearly traveling belt. It should be understood that the invention of the appended claims is not limited to the exact details of design and construction described herein, for obvious changes and modifications within the scope of the claims, will be apparent to those skilled in the art.

It is claimed and desired to secure by Letters Patent:

1. A dielectric drier for baking the moisture out of moist objects comprising relatively adjustable electrodes to be energized by a high frequency voltage, supporting means for said electrodes, means mounted on said supporting means for adjusting the spacing between said electrodes to accommodate varying sizes of moist objects, movable means associated with one of said electrodes for introducing said objects between said electrodes, exhaust means mounted on said supporting means, said exhaust means comprising a movable intake element having at least one opening positioned a predetermined distance from another of said electrodes for removing from between said electrodes the moisture driven ofi from said objects upon energization of said electrodes, and means including said adjusting means for maintaining said intake element opening at said predetermined distance from said another of said electrodes for all spacings of said electrodes.

2. A dielectric drier for baking the moisture out of moist objects comprising supporting means, relatively movable electrodes to be energized by a high frequency voltage, means mounted on said supporting means for adjusting the spacing between said electrodes to accommodate various sizes of objects, movable means associated with one of said electrodes for introducing said objects between said electrodes, a moisture barrier and condensation-inhibiting means mounted on another of said electrodes, exhaust means mounted on said supporting means, said exhaust means comprising a movable intake element having an opening adjacent said barrier means and at a predetermined distance therefrom, said opening cooperating with said barrier means to remove from between said electrodes substantially 10 all the moisture driven off from said objects upon energization of said electrodes, and means including said adjusting means for maintaining said intake element opening in the same relative predetermined position adjacent said barriermeans for all spacings of said electrodes.

3, A dielectric drier for baking the moisture out of moist objects comprising longitudinally extending supporting means, relatively adjustable planar electrodes extending longitudinally of said supporting means, said electrodes to be energized by a high frequency voltage, means mounted on said supporting means for adjusting the spacing between said electrodes to accommodate varying sizes of moist objects, means associated with one. of said electrodes and movable relative to said supporting means for introducing said objects between said electrodes, exhaust means mounted on said supporting means, said exhaust means'come prising a movable intake element having an opening extending longitudinally of said supporting means for at least a portion of the length of another of said electrodes and positioned a pre determined distance from said another of said;

electrodes for removing from. between said electrodes substantially all the moisture driven off from said objects upon energization of said electrodes, and means including said adjusting means for maintaining said intake element opening in the same relative predetermined position adjacent said another of said electrodes for all spacings of said electrodes.

4 A dielectric drier for baking the moisture out of moist objects comprising relatively adjustable electrodes to be energized by a high frequency voltage, supporting means for said electrodes, means mounted on said supporting means for adjusting the spacing between said electrodes to accommodate varying sizes of moist objects, movable means associated with one of said electrodes for introducing said objects between said electrodes, and exhaust means mounted on said supporting means, said exhaust means comprising at least one movable intake element havin at least one aperture opening on the underside of another of said electrodes for removing from between said electrodes the moisture driven olT from said objects upon energization of said electrodes, and means including said adjusting means for maintaining said aperture opening on the underside of said another of said electrodes for all spacings of said electrodes.

5. A dielectric drier for baking the moisture out of moist objects comp-rising a pair of relatively movable electrodes to be energized by a high frequency voltage, supporting means for said electrodes, means mounted on said supporting means for adjusting the spacing between said electrodes to accommodate varying sizes of moist objects, movable means associated with one of said electrodes for introducing said objects between said electrodes, exhaust means mounted on said supporting means, said exhaust means comprising an intake element mounted on the other of said electrodes for movement therewith and having at least one opening adjacent at least one edge of said other electrode for all spacings of said electrodes for removing from between said electrodes the moisture driven off from said objects upon energization of said electrodes.

6. A dielectric drier for baking the moisture out of moist objects comprising relatively adjustable electrodes to be energized by a high frequency voltage, supporting means for said electrodes, adjusting means mounted on said supporting means for varying the spacing between said electrodes to accommodate varying sizes of objects, means associated with one of said electrodes for introducing said objects between said electrodes, and exhaust means mounted on said supporting means, said exhaust means comprising intake means mounted on another of said electrodes, said intake means partially enclosing said another electrode and forming with said another electrode exhaust passageways having openings adjacent the edges of said electrode for the withdrawal of moisture driven ofi from said objects upon energization of said electrodes, and insulating means mounted on said manifold for extending the leakage path between said intake means and said exhaust means for all spacings of said electrodes.

'7. A dielectric drier for baking the moisture out of moist objects comprising relatively adjustable electrodes to be energized by a high frequency voltage, supporting means for said electrodes, adjusting means mounted on said support ing means for varying the spacing between said electrodes to accommodate varying sizes of objects, means associated with one of said electrodes REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,042,145 Darrah May 26, 1936 2,428,615 Brown Oct. '7, 1947 2,436,732 Rowe Feb. 24, 1948 2,485,609 Koster et a1 Oct. 25, 1949 

